Blockchain applications for the Internet of Things: Systematic review and challenges

•We investigate and analyze the BC technologies in terms of fundamental features, and ledger systems.•We give an overview of BC basics, its key features, and how they can be leveraged for IoT.•This study helps to remove restrictions in the implementation of BCIoT applications.•We discuss the integration schemes of BC and IoT, which can help develop a new system based on a decentralized method.•We identify and outline open research issues and challenges in adopting and leveraging BC features for IoT.